Pathogens: Monilinia fructicola, Botrytis cinerea, Rhizopus spp.

Ripe fruit rot caused by Monilinia or Botrytis results in firm, circular spots that spread rapidly over fruit. Monilinia causes dark brown lesions on
fruit that eventually turn black from the development of pseudosclerotia
(fungal tissue), whereas Botrytis causes light tan to grayish lesions with gray spores. Spore masses may grow on
the rotted areas. Fruit becomes more susceptible as it ripens. Botrytis-diseased fruit usually do not
remain on the tree until next season, but they are present as inoculum sources
for the current season's crop. When Monilinia-diseased
fruit remain on the tree, they are known as mummies.

Rhizopus rot is a postharvest storage
problem. The decaying fruit tissue is watery and soft; the fungus is identified
by masses of white mycelium with tiny black sporangia that form most abundantly
on fruit near the edge of containers.

Monilinia and Botrytis can infect
uninjured ripening fruit and cause green fruit rot and incipient infections of
young fruit. Wetness, either rain or dew, and injury or fruit cracking
increases preharvest infection and subsequent rot. Rhizopus spp. invades only ripe fruit that have been injured and
the decay is a postharvest concern only.

Fruit rot is managed by controlling blossom and twig
blight in spring, removing blighted twigs when possible, using appropriate
levels of nitrogen fertilizer and water, removing or turning under thinned
fruit, controlling fruit-feeding insects such as peach twig borer and oriental
fruit moth, and making preharvest treatments when necessary. Early maturing
cultivars typically have little trouble with ripe fruit rot.

Take fruit samples every other week after
color break (see PREHARVEST FRUIT SAMPLES) to
detect any developing problems in the orchard and a fruit damage sample at
harvest to assess the effectiveness of the current year's IPM program and to
determine the needs of next year's program, see FRUIT EVALUATION AT HARVEST. Record results(115 KB, PDF) for
harvest sample.

Organically
Acceptable Methods
Treatments of sulfur dust
are acceptable for use in an organically certified crop.

Chemical
Control
Fungicides are preventive,
not eradicative; they must be applied to uninjured fruit before infections
occur. Injured fruit cannot be protected from Monilinia or Botrytis rot
by preharvest sprays. Preharvest sprays for Monilinia should be applied as needed during the last 4 weeks before harvest. Where Rhizopus fruit rot is a problem, treat
10 days to 1 day before harvest. After harvest, Rhizopus can be controlled by storing the crop at temperatures
below 40°F.

Common name

Amount per acre

REI‡

PHI‡

(Example trade name)

(hours)

(days)

UPDATED: 9/15

When choosing a pesticide, consider its usefulness in an IPM program by reviewing the pesticide’s properties, efficacy, application timing, and information relating to resistance management, honey bees(PDF), and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.

COMMENTS: One application only per season and always apply with a companion fungicide with a different mode of action group number. Strains of brown rot resistant to thiophanate methyl have been found in California. If resistance has occurred in your orchard, do not use this fungicide.

COMMENTS: Do not apply more than 6 lb/acre per season and avoid making more than 2 consecutive applications of this material.

H.

MYCLOBUTANIL

(Rally 40WSP)

2.5–6 oz

24

0

MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)

I.

CAPTAN

(Captan 50WP)

4–8 lb

24

0

MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)

COMMENTS: Do not apply in combination with, immediately before, or closely following oil sprays.

J.

SULFUR DUST#

50 lb

See label

See label

MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M2)

COMMENTS: Do not apply within 3 weeks of an oil application.

POSTHARVEST

A.

FLUDIOXONIL

(Scholar)

8–16 oz/100 gal water

NA

NA

MODE-OF-ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12)

COMMENTS: Treats 200,000 lb fruit using a spray-application system.

‡

Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.

#

Acceptable for use on organically grown produce.

1

Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1,4,9,11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to a fungicide with a different mode of action Group number.

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